Ostracods of genus Cyprideis, especially the species Cyprideis torosa, are considered very useful for paleoenvironmental interpretations due to their strong adaptability to salinity changes and their intense ecophenotypic plasticity. This study concerns the morphological variability of Cyprideis populations from Quaternary marginal marine sediments of Greece, focusing on C. torosa. In particular, C. torosa specimens of Holocene and Pleistocene age were collected from four different sedimentary archives (Piraeus coastal plain, Southern Evoikos Gulf, Vravron coastal plain and Corinth Isthmus) and a modern environment (Vravron coastal marsh), provided a detailed insight into the presence of this model-ostracod taxon in Greek palaeo-/environments. The objective is to describe and morphology of C. torosa from Greece, and test if the results of previous studies on the morphology of recent specimens (size, sieve pores and ornamentation of the external surface of the valves) could be applied to fossil associations. Furthermore, specimens of a unique Cyprideis species retrieved from the Pleistocene of Corinth Isthmus were examined. A total of 1.161 valves of C. torosa, both female (left and right ones) and male (left and right ones), were collected and measured through stereoscope in terms of maximum length and height, while their external surfaces were also examined in detail through the means of electron microscopy. Furthermore, 131 valves of the Cyprideis species from the Pleistocene (Calabrian) outcrop of the Corinthian Marl were measured, described and compared to C. torosa populations. This species was first reported by Tsourou et al. (2021), and it is presented in more detail here. Overall, the results show that variations in valve size of C. torosa could be correlated with salinity changes, as it seems that there is trend for larger valves with decreasing salinity, but it is not that clear as, in most cases, the differences in size are not that intense. The larger C. torosa valves that were observed are the ones from the Chibanian mesohaline lagoon (retrieved from the Corinthian marl), while the smallest valves came from the Piraeus Holocene shallow coastal marine palaeoenvironment, which are the samples representing the highest salinity out in all the studied samples. Concluding, it seems that the size of C. torosa could be related to changes of the salinity in lagoonal environments, but further data from other C. torosa populations need to be incorporated in this dataset. The proportion of rounded sieve pores increases with decreasing salinity, as previous studies have suggested and accordingly, ornamentation increases with decreasing salinity: from smooth to punctuated and reticulated valves. Both support the hypothesis that morphological characteristics of C. torosa should be considered an equally important factor to accompanying fauna in detailed palaeoenvironmental interpretations.
Κωνσταντίνος Γ. Γούκος (2025) studied this question.